You have a wonderful memory! Yes, a film of the "faces" of convicts was projected onto the face of dummies, and it appeared as if the dummys were "live" singing "you might get out if the mine don't flood!" I sometimes worked at the flooded mine as a convict in the early 80s, and the "citizens" behind those faces were Elmer (Can't remember Elmer's last name) and Wayne Milnes from the street troupe. Due to humid conditions, the projectors broke down a lot. Kerry, our maintenance guy at the diving bell, was responsible for keeping the projectors in working order. My guess is they moved away from those talking dummys because of the frequent break downs and hassles with keeping things up and running. But it's just my guess, I don't really know why that has happened.